All gypsum deposits belong to one of three categories:
- Sedimentary deposits
- Residual deposits
- Metasomatic deposits.
According to the conditions of their formation, sedimentary deposits are divided into:
- syngenetic (the rock and the embedded gypsum formed simultaneously)
- epigenetic (the result of anhydrite hydration process triggered by groundwater).
In deposits of the first type, gypsum takes the form of lenses and layers up to 20 m thick or more.
In deposits of the second type, the layered gypsum structure is complicated by internal tectonics, folding, upswelling and wedging-out.
Gypsum deposits in Russia are almost always of sedimentary type.
Residual deposits (accumulation of gypsum during leaching of minerals in salines) and metasomatic deposits (replacement of carbonate rocks with gypsum under the influence of sulfuric acid waters) are practically unknown to the Russian gypsum industry.
From the point of view of geology, Russian gypsum deposits used by the industry are located in the sedimentary layers of the Cambrian, Devonian, Carboniferous, Permian, Jurassic, and Quaternary periods. The Carboniferous period accounts for more than 55% of the reserves, followed by the Permian (32%) and Devonian (10%) periods.
According to the calculation carried out in 2003, the state register of gypsum reserves accounts for 3275.9 million tons. Of all deposits included in the calculation, 24 (28%) are being developed.
As can be seen from the table, the bulk (more than half) of the gypsum reserves is concentrated in the Central Federal District, where the 6 largest deposits are located. The Volga and Southern Federal Districts also have significant reserves of gypsum raw materials (a third of the country's reserves in total).
In total, there are 86 gypsum deposits in Russia, most of which are small-scale reserves. 90% of gypsum is mined at 19 largest deposits with reserves of more than 25 million tons.
Nine largest gypsum deposits in Russia (with reserves of more than 100 million tons each) are Novomoskovskoye, Pavlovskoye, Skuratovskoye, Bolohovskoye, Pletnevskoye, Baskunchakskoye, Lazinskoye, Poretskoye, and Obolenskoye. They account for 75% of all production. Most deposits contain a mixture of gypsum (up to 90%) and anhydrite.
For reference, the explored global reserves of gypsum exceed 7,500 million tons. In other words, half of the world's reserves are located in Russia. At the same time, the production of gypsum raw materials in the world is about 110 million tons per year. Russia produces about 6 million tons annually — that is, 5-6% of world production. Moreover, Russian gypsum reserves allow for a significant increase in production in the future.